Cobalamin (vitamin B12) is a cobalt-containing enzymatic cofactor involved in methionine synthesis. Provided only by select bacteria and archaea in marine systems, this vitamin is known to limit primary production in different oceanic areas. Understanding the consequences of cobalamin limitation on phytoplankton physiology is of great interest, notably for cobalamin-dependent haptophytes that significantly contribute to oceanic carbon fixation and sulfur cycle through dimethyl sulfonio propionate (DMSP) synthesis. Here, the effect of cobalamin limitation was compared to nitrogen limitation on the model haptophyte Tisochrysis lutea grown in chemostats, combining comparative proteomics with the analysis of major macromolecules and specific osmolytes. Our results highlight the interconnection of carbon and DMSP metabolisms through the cobalamin-dependent methionine synthesis by showing that cobalamin scarcity impacts the mechanisms of carbon allocation and reduces DMSP quota. Conversely, proline production seemed to anticorrelate with cobalamin availability. In a boarder context, analysis of transcriptomes or genomes of main DMSP producers from different phytoplankton lineages suggests that most of them are cobalamin-dependent, which means that prokaryotic cobalamin synthesis exerts an important control on phytoplankton DMSP production in some regions of the world ocean.

中文翻译：

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钴胺素稀缺改变了碳分配并通过触须植物微藻 Tisochrysis lutea 中的甲硫氨酸代谢损害了 DMSP 的产生

钴胺素（维生素 B12）是一种参与蛋氨酸合成的含钴酶辅因子。仅由海洋系统中的特定细菌和古细菌提供，这种维生素已知会限制不同海洋区域的初级生产。了解钴胺素限制对浮游植物生理学的影响非常有趣，特别是对于通过丙酸二甲酯 (DMSP) 合成显着促进海洋碳固定和硫循环的钴胺素依赖型触生植物。在这里，将比较蛋白质组学与主要大分子和特定渗透物的分析相结合，将钴胺素限制的影响与氮限制对在恒化器中生长的模型触手植物 Tisochrysis lutea 进行了比较。我们的结果通过显示钴胺素稀缺影响碳分配机制并减少 DMSP 配额，突出了碳和 DMSP 代谢通过钴胺素依赖性蛋氨酸合成的相互联系。相反，脯氨酸的产生似乎与钴胺素的可用性呈反相关。在更广泛的背景下，对来自不同浮游植物谱系的主要 DMSP 生产者的转录组或基因组的分析表明，它们中的大多数是钴胺素依赖性的，这意味着原核钴胺素合成对世界海洋某些地区的浮游植物 DMSP 生产产生重要控制。